<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>JS-引入方式</title>
</head>
<body>


  <!-- <script>
  //1. 内部脚本
  alert('Hello JS');
  </script> -->
  <!-- 2. 外部脚本 -->
   <script src="js/demo.js"></script>
</body>
</html>